The most common embodiment of passenger car automatic transmissions is a so-called torque converter transmission that differs from conventional and automated shifting transmissions primarily by a shifting process that does not interrupt the tensile force. Such passenger car automatic transmissions usually have a hydraulic torque converter as a starter clutch and are comprised essentially of several multiple-disk clutches and a combination of several freewheels and planetary gears. All shifting and coupling processes are here performed via the multiple-disk clutches that produce the non-positive connection of the individual planetary gear stages to the input and output shafts of the automatic transmission.
Because considerable axial forces are also applied between the transmission parts during the individual shifting processes due to the typical helical gearing of the planetary wheels of the planetary gear, in modern automatic transmissions, for preventing friction losses and reduced efficiency, the individual clutch and planet carriers are supported relative to each other by a plurality of axial needle bearings. In special cases, individual planet carriers rotating in one direction in a planetary gear must be supported axially relative to each other against individual planet carriers rotating in the other direction in an adjacent planetary gear. Such a known bearing between the sun wheel carrier of a first planetary gear and the adjacent internal gear tip of a second planetary gear in a passenger car automatic transmission is shown as an example in FIG. 1 of the accompanying drawings and is formed essentially of the two rotating carrier components 1, 2 with circular ring-shaped end faces 3, 4 that face each other and between which an axial roller bearing 5 is arranged. Here, the axial roller bearing 5 has a first ring-shaped angled disk 6 made from a thin steel sheet contacting the end face 3 of the first carrier component 1 and a second ring-shaped angled disk 7 made from a thin steel sheet contacting the end face 4 of the second carrier component 2, as well as a needle cage 10 that rolls between the axial inner sides 8, 9 of the angled disks 6, 7 and is formed by a plurality of bearing needles 12 arranged one next to the other and held at equal distances from each other by a bearing cage 11 and is lubricated and cooled by a lubricant flow 13 emerging from a shaft guided centrally through the axial roller bearing 5.
One special feature of axial roller bearings 5 arranged in this way is that these have high differential rotational speeds resulting from the different directions of rotation of the adjacent planet carriers 1, 2 also in the no-load state and therefore require sufficient lubrication and cooling also in the no-load state. In practice, however, it has been shown that under such no-load conditions, a radial ring gap 15 resulting from the axial play of the axial roller bearing 5 is produced between the first carrier component 1 and the first angled disk 6, through which the majority of the lubricant flow 13 emerging from the shaft guided centrally through the axial roller bearing 5 escapes, so that the axial roller bearing 5 is no longer adequately lubricated and cooled. The insufficient lubrication consequently leads to overheating and bearing damage that might cause a failure of the entire automatic transmission.